Wiktionary
a. Without a helmet
Usage examples of "helmetless".
With a sudden crackling of underbrush, a wild-eyed, helmetless soldier tore into the tiny glade.
They left him helmetless, so that even if by some miracle he got free of his bonds he would be unable to leave the dome and return to his ship.
A soldier appeared, helmetless, his young face white, his eyes fixed on Baudin, his steps ceasing.
Confronted by that quietly happy gaze, Harry, unarmed and helmetless, unable to protect his head or to radio for help, his own weapon hopelessly out of reach, jumped up and dodged and sprinted around a curving corner into the other wing of the social room.
The Gardac left his post and went into the guardhouse, returning with a helmetless yeoman who scratched a long scab on his face.
As the pirates streamed down into the fray Axis turned to see Baron Ysgryff, helmetless now, grinning at him.
Even as the troops are pouring out of the trailer, a helmetless man throws open the passenger's-side door on the truck cab and jumps to the pavement.